Myelin imaging measures as predictors of cognitive impairment in MS patients: A hybrid PET-MRI study

•Different imaging techniques (DTI, MTR and 11C-PIB PET) were compared.•All images from one subject were acquired simultaneously in a PET/MR hybrid system.•Low MTR in thalamus and corpus callosum were predictors of cognitive impairment in the entire MS cohort.•DTI showed association in PMS, while MTR and 11C-PIB uptake (DVR) in RRMS.•11C-PIB PET was a method more consistently associated with cognitive parameters. Cognitive impairment is one of the concerns of Multiple Sclerosis (MS) and has been related to myelin loss. Different neuroimaging methods have been used to quantify myelin and relate it to cognitive dysfunctions, among them Magnetization Transfer Ratio (MTR), Diffusion Tensor Imaging (DTI), and, more recently, Positron Emission Tomography (PET) with 11C-PIB. To investigate different myelin imaging modalities as predictors of cognitive dysfunction. Fifty-one MS patients and 24 healthy controls underwent clinical and neuropsychological assessment and MTR, DTI (Axial Diffusion-AD and Fractional Anisotropy-FA maps), and 11C-PIB PET images in a PET/MR hybrid system. MTR and DTI(FA) differed in patients with or without cognitive impairment. There was an association of DTI(FA) and DTI(AD) with cognition and psychomotor speed for progressive MS, and of 11C-PIB uptake and MTR for relapsing-remitting MS. MTR in the Thalamus (β= -0.51, p = 0.021) and Corpus Callosum (β= -0.24, p = 0.033) were predictive of cognitive impairment. DTI-FA in the Caudate (β= -26.93, p = 0.006) presented abnormal predictive result. Lower myelin content by 11C-PIB uptake was associated with worse cognitive status. MTR was predictive of cognitive impairment in MS.